Mechanical properties of double-sine-Gordon solitons and the application to anisotropic Heisenberg ferromagnetic chains

Abstract

The classical spin dynamics of an anisotropic Heisenberg ferromagnetic chain in an applied magnetic field is approximately mapped onto the double-sine-Gordon model. Depending on the values of the parameters, this model is capable of supporting a variety of interesting nonlinear phenomena. Among others, we find solitons which behave as true domain walls, thus resulting in very long correlation lengths at low temperature, solitons that are broadly extended in space, metastable states whose lifetimes can be controlled continuously from $0 \mathrm{to} \infty$, a ground state which undergoes a pitchfork bifurcation with changing magnetic fields, and solitons which can combine or dissociate spontaneously as the parameters are varied, into new solitons, while conserving both creation energies and topological charges.